Fix some warnings by cppcheck

Warning message:
```
ikvm_manager.hpp:26:5: style: Class 'Manager' has a constructor with
1 argument that is not explicit. [noExplicitConstructor]
    Manager(const Args& args);
    ^
```

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I993565998eebfa7ab7447b05f50ac627c9f41060
diff --git a/ikvm_manager.hpp b/ikvm_manager.hpp
index c6750e6..9b246c4 100644
--- a/ikvm_manager.hpp
+++ b/ikvm_manager.hpp
@@ -23,7 +23,7 @@
      *
      * @param[in] args - Reference to Args object
      */
-    Manager(const Args& args);
+    explicit Manager(const Args& args);
     ~Manager() = default;
     Manager(const Manager&) = default;
     Manager& operator=(const Manager&) = default;